Effects of Nitrogen on the Dry Matter,Nitrogen Accumulation and Distribution of Cotton under Short-term Soil Drought during the Flowering and Boll-forming Stage

Effects of nitrogen on the dry matter weight,nitrogen accumulation and distribution,yield and fiber quality of cotton under short-term drought and after re-watering during flowering and boll-forming stage were studied.Pot experiments were conducted to short-term drought in 2005 and 2006 at the research field area of Nanjing Agricultural University.Within each water treatment,three nitrogen levels were imposed:0,240 and 480 kg N·hm-2.According to data,soil drought significantly reduced dry matter weight,nitrogen accumulation,yield and fiber quality of cotton,but increased N content in different organs of cotton,compared with well-water treatments.Drought reduced the distributive indices of dry matter weight and nitrogen accumulation in leaf,but increased the distributive indices of dry matter weight and nitrogen accumulation in root,and increased the ratio of root dry matter/shoot dry matter and root N accumulation/shoot N accumulation of cotton.Nitrogen increased dry matter weight and N accumulation in cotton,and augmented the water stress indices under drought stress.There was notability compensative growth for cotton after re-watering,especially for root,the dry matter weight and nitrogen accumulation in root of drought treatments were higher than that of well-water treatments.Nitrogen could enhance the compensative capacity.The dry matter weight of reproductive organs,cotton yield and fiber quality were all highest at 240 kg N·hm-2 level under drought and after soil re-watering.These results suggest that 240 kg N·hm-2 is the optimal nitrogen application rate under short-term drought in our experiments,deficient(0 kg N·hm-2) and excessive nitrogen supply(480 kg N·hm-2) are disadvantaged to the yield and fiber quality.